Changes in total carboxylation reactions in isolated hepatocytes prepared from animals fed diets deficient in protein will be compared with those obtained from rats fed a protein sufficient diet. Quantitative changes in hepatic mRNA for malic enzyme will also be measured in these animals. The effects of dietary supplementation with pure L-amino acids on the induction of hepatic malic enzyme caused by severe protein restriction will also be investigated. It is also proposed to study changes in lipogenic enzymes (malic enzyme, fatty acid synthetase system, glucose-6-phosphate dehydrogenase, citrate cleavage enzyme) in primary cultures of rat hepatocytes under the influence of glucagon and insulin in order to investigate the mode of action of these hormones in the regulation of protein steady-state in liver.